The superiority of optical signal in the aspects of bandwidth, security and other physical characteristics, compared to the electrical signal, has made optical fiber a popular choice for signal transmission, in particular, for communication or multimedia applications. FIG. 1 shows a schematic view of a typical optical fiber. As shown in FIG. 1, A typical optical fiber includes a glass core 101, a cladding layer 102 and a buffer layer 103. Glass core 101 is the part where the optical signal actually travels. Because glass core 101, cladding layer 102 is extremely fragile and susceptible to the surface abrasion, buffer layer 103 are needed to provide protection to glass core 101. In particular, during deployment, the field termination must be performed on the optical fiber for extension or connection to other optical devices or elements. The field termination is a process includes at least the steps of: stripping the buffer layer; cleaning the stripped surface with alcohol or other solvent to remove any buffer coating remaining and debris; cleaving the terminal of the optical fiber according to specification; and performing connection through thermal splice or other mechanical means. It is worth noting that the field termination process is relative delicate task and the optical fiber is susceptible to damages caused by errors, such as, inappropriate tool and parameter adjustment, dust and other abrasion source, human error, and so on. Once damaged, the quality and the life span of the optical fiber are severely affected.
A typical field termination usually employs factory pre-polished optical connector to eliminate the need for hand polishing in the field. U.S. Pat. No. 7,280,733 disclosed a field termination optical connector, and U.S. Pat. No. 5,159,653 disclosed a mechanical splice technology. Although different manufacturers may employ different means to splice the optical fiber, the common part of the mechanical splice is to clamp on the cladding layer of the optical fiber.
Alternative optical fiber structures are developed to address the strength issue of the fiber optical. For example, U.S. Pat. No. 4,682,850 disclosed an optical fiber with single ultraviolet cured resin coating, applicable in particular to loosely wrapped cable structure. The resin coating has a thickness of about 62.5 um and the total diameter of the optical fiber is of 250 um. The thickness of resin coating is preferably no less than 50 um. The resin has a Shore A hardness of about 70 to 75.
Taiwan Patent No. I326773 disclosed an improved optical fiber structure and the manufacturing method thereof, wherein the glass comprises a plurality of microstructures formed therein to lower the risk of snapping when the optical fiber is subjected to bending by external force.
However, while the above structures provide possible solution to enhance the strength of the optical fiber, these techniques do not address the difficult issue of field termination.
U.S. Pat. No. 5,381,504 (Re. 36,146) disclosed an optical fiber element including an optical fiber having a numerical aperture ranging from 0.08 to 0.34 and a protective coating affixed to the outer surface of the optical fiber and remaining on the optical fiber during connection. As shown in FIG. 2, protective coating 101A has a thickness ranging from 8 to 23 um and a combined diameter ranging from about 120 to about 130 um. The total of the optical fiber element ranges about 240 to about 260 um. The protective coating has a Shore D [hardness] value of 65 or more. While the optical fiber structure address the issue of connection, one disadvantage of the mentioned structure is that a special cleaver is needed to perform the necessary cleaving so that the cladding layer would be slightly cleaved to enable subsequent snapping of the glass core. An alternative is for the engineer to re-adjust the cleaving thickness of the cleaver. Neither of the above two cleaving alternatives is satisfactory and may impede the optical fiber deployment efficiency and quality.
It is therefore imperative to devise an optical fiber structure to facilitate the field termination process, the deployment quality and efficiency issues.